(a) Field of the Invention
The present invention relates to a novel high polymer, a ferroelectric liquid-crystalline composition containing the high polymer and a raw material of the high polymer, more particularly, to a novel high polymer and a ferroelectric liquid-crystalline composition containing the same, which is useful in the field of optoelectronics, for example, as an element of liquid crystal devices which are incorporated into digital display devices of desk calculators and watches and clocks, dot-matrix display devices, electronic optical shutters, electronic optical diaphragms, optical modulators, optical-path transfer switches in optical communication systems, memory storages, liquid crystal printer heads and varifocal lenses.
(b) Description of the Related Art
Display devices produced by using low molecular weight liquid-crystalline compounds have been widely used, for example, for the digital display of desk calculators, watches and clocks. In these application fields, the conventional low molecular weight liquid-crystalline compounds generally are disposed between two glass substrates which are spaced out in the order of microns. In the production of large screens or curved screens, such an adjustment of the space, however, has been impossible.
To solve the problem, It has been attempted to develop polymeric liquid crystals, which are moldable in themselves [e.g., J. Polym. Sci., Polym. Lett., Ed. 13, 243(1975), Polym. Bull. 6, 309(1982), Japanese Patent Application Kokai Koho (Laid-open) No. 56-21479]. These conventional polymeric liquid crystalline compounds, however, are disadvantageous in that they cannot exhibit liquid-crystalline properties at room temperature and require heating at a temperature not lower than their glass transition temperatures and lower than their clearing points to form liquid-crystalline mesophases.
Japanese Patent Application Kokai Koho (Laid-open) No. 63-99204 discloses the synthesis of polyacrylate Ferroelectric, polymeric liquid-crystalline compounds, which are reported to exhibit excellent properties as compared to the above-described polymeric liquid-crystalline compounds. Even these conventional side chain ferroelectric, polymeric liquid-crystalline compounds are not satisfactory in the response speed and operable temperature range.
Japanese Patent Application Kokai Koho (Laid-open) No. 63-254529 discloses polyether ferroelectric, polymeric liquid-crystalline compounds, which are prepared by polymerizing epoxy monomers having optically active groups [for example, polymeric liquid-crystalline compounds which have the repeating units represented by formula ( IV') and prepared by polymerizing the epoxy compound represented by Formula (IV), u in the formulas (IV) and (IV') being an integer of 1 to 30]. ##STR2##
The pamphlet of International Publication No. 92/01731 discloses polymeric liquid-crystalline compounds which have repeating units whose side chains contain aromatic rings and whose main chains comprise a linear hydrocarbon structure and a siloxane structure, for example, the one represented by the following formula (V). ##STR3##
Although these conventional side chain ferroelectric, polymeric liquid-crystalline compounds have an advantage of responding against the stimulus of external electric field over a wide range of temperatures including room temperature, the response speed is still too slow for practical use.
There is a report of polymeric liquid-crystalline compositions which comprise low molecular weight liquid-crystalline compounds and polymeric liquid-crystalline compounds having asymmetric carbon atoms [Japanese Patent Application Kokai Koho (Laid-open) No. 63-284291]. However, the side chain polymeric liquid-crystalline compounds exemplified therein do not provide a sufficient space between side chains due to their conventional acrylate or siloxane main chains, and increasing their molecular weight disables the mixing of a large amount of low molecular weight liquid-crystalline compounds, making the speeding up of response speed difficult. This means that it is difficult to combine in such compositions a fast response and the advantages of high polymers.
As to the attempts of preparing compositions which have the merits of high polymers and as well exhibit a fast response by mixing non-liquid-crystalline, polymeric compounds and low molecular weight liquid-crystalline compounds, Japanese Patent Application Kokai Koho (Laid-open) No. 61-47427 discloses compositions which were endowed with an ability of self-form retaining by mixing low molecular weight liquid-crystalline compounds with non-liquid-crystalline high polymers. Since in these compositions, liquid crystal areas are dispersed in the matrix of the polymeric compounds (resins), there is a possibility that allowing the compositions to stand for a long time causes the separation of the low molecular weight liquid-crystalline compounds. Further, the compositions cannot exhibit sufficient contrast since the dispersed low molecular weight liquid-crystalline compounds form islands, and the dispersion system makes the control of orientation difficult. Japanese Patent Application Kokai Koho (Laid-open) Nos. 62-260859 and 62-260841 disclose ferroelectric composite film which contains low molecular weight liquid-crystalline compounds and thermoplastic resins which are compatible with the low molecular weight liquid-crystalline compounds. However, it is difficult to select low molecular weight liquid-crystalline compounds and thermoplastic resins which are compatible with each other, and the control of orientation is also difficult. There is another problem that the low molecular weight liquid-crystalline compounds should have ferroelectricity. Japanese Patent Application Kokai Koho (Laid-open) No. 1-198683 discloses compositions which comprise high polymers containing proton donors (or proton acceptors) and low molecular weight liquid-crystalline compounds containing proton acceptors (or proton donors). However, there is a problem that the structures of the high polymers and the low molecular weight liquid-crystalline compounds are considerably limited due to the essential condition that they should contain proton donors or proton acceptors.